1. Field of the Invention
This invention relates generally to the formation of a tungsten plug and more particularly, it relates to the formation of a barrier layer utilizing tungsten nitride prior to the chemical vapor deposition (CVD) of tungsten in a single chamber used for manufacturing a tungsten plug, for forming a contact gate in Flash EEPROM memory devices, and for forming local interconnects to CMOS gate structures.
2. Description of the Prior Art
As is generally well-known in the art of manufacturing of integrated circuits, a barrier layer is often required to be formed to prevent the diffusion of one type of material to another type of an adjacent material. In the past, titanium nitride (TN) had been used as the material for forming the diffusion barrier layer where conductive interfaces are needed to be maintained.
For example, in a conventional tungsten plug formation process, a sputtering or chemical vapor deposition (CVD) process is used for the formation of a titanium nitride layer on a substrate having a contact hole formed therein prior to the CVD of tungsten to fill the contact hole. However, since two different film formation processes are involved, there is required a first type of equipment for use in the deposition of the titanium nitride and a second different type of equipment for use in the deposition of the tungsten. As a result, the use of these two different process steps increases significantly the cost for the conventional tungsten plug formation process. In addition, in the formation of the conventional tungsten plug there is required a first subsequent process step to remove the tungsten and a second subsequent process step to remove the titanium nitride on the field region in order to form the tungsten plug, such as etching back and chemical-mechanical polishing (CMP). Therefore, since different chemistry is used in these removal steps, this also leads to a complicated process sequence.
It is apparent from the foregoing discussion that there still exists a need for a tungsten plug formation process, which requires only a single deposition chamber so as to reduce significantly the processing cost. This is achieved in the present invention by the formation of tungsten nitride by a plasma-enhanced CVD to be used as the barrier metal instead of titanium nitride, which is followed by a blanket tungsten film CVD made in the same deposition chamber.